During and after cardiac surgery, it is of interest to monitor the performance of the heart, especially the responses to various forms of treatment.
One way to obtain data related to various aspects of the performance of the heart is by a motion sensor on or in the heart to measure the movement of the heart wall. A number of references describe the use of such motion sensors to obtain data related to specific performance parameters.
WO 03/061473 describes the use of an accelerometer fastened on a surface part of a heart to detect the movements of this surface part, e.g. in order to detect ischemia in this surface part.
U.S. Pat. No. 5,628,777 describes motion sensors integrated in large patches or electrodes having the function of delivering electrical stimulation signals, i.e. pacing the heart. The signals from the motion sensors are used to detect arrhythmia in order to trigger deliverance of the electrical stimulation signals.
U.S. Pat. No. 7,139,609 describes derivation of parameters representative of heart function, such as stroke volume, cardiac output, blood pressure, from acceleration signals representative of the acceleration of tissue within the patient.
In today's setup, a lot of data obtained from different individual apparatus are presented to the surgeon or cardiologist, who can thereby get a feeling for the global heart function and its response to an applied treatment. In order to simplify the equipment and provide a more objective estimate of the global heart function, an improved scenario for estimating changes in cardiac pumping capacity would be advantageous.